From: David Miller <davem@davemloft.net>
To: ast@plumgrid.com
Cc: mingo@kernel.org, torvalds@linux-foundation.org,
luto@amacapital.net, dborkman@redhat.com,
hannes@stressinduktion.org, chema@google.com,
edumazet@google.com, a.p.zijlstra@chello.nl, pablo@netfilter.org,
hpa@zytor.com, akpm@linux-foundation.org, keescook@chromium.org,
linux-api@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v12 net-next 03/11] bpf: add lookup/update/delete/iterate methods to BPF maps
Date: Tue, 16 Sep 2014 16:54:52 -0400 (EDT) [thread overview]
Message-ID: <20140916.165452.1747695341192703967.davem@davemloft.net> (raw)
In-Reply-To: <CAMEtUuxp6709mdygiQyCqwjv-0kF-CbNOzCCZmKw_mUckF4NZA@mail.gmail.com>
From: Alexei Starovoitov <ast@plumgrid.com>
Date: Tue, 16 Sep 2014 13:44:12 -0700
> the union indeed changes alignment from patch #1 to #3,
> but, imo, it is not a problem, since kernel does:
It changes the alignment of the datastructures in userspace.
> I haven't thought of 'aligned_u64' for this case.
> For counters and masks it would be perfect, but here user is
> passing real pointers to key and value, so they have to
> be 'void __user *', otherwise user would need to type cast
> them, which I want to avoid.
The cost of the compat layer must be considered and weighted
against this cast, which I think is really no big deal.
> I think compat layer is a better option.
It's overhead you'll have to support forever, I think you should
reconsider.
All of the "ugly casting" will be hidden, or can be hidden, in the
syscall wrappers and/or interfaces in userspace.
next prev parent reply other threads:[~2014-09-16 20:54 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-15 19:18 [PATCH v12 net-next 00/11] eBPF syscall, verifier, testsuite Alexei Starovoitov
2014-09-15 19:18 ` [PATCH v12 net-next 01/11] bpf: introduce BPF syscall and maps Alexei Starovoitov
2014-09-15 19:18 ` [PATCH v12 net-next 02/11] bpf: enable bpf syscall on x64 and i386 Alexei Starovoitov
2014-09-15 19:18 ` [PATCH v12 net-next 03/11] bpf: add lookup/update/delete/iterate methods to BPF maps Alexei Starovoitov
2014-09-16 19:16 ` David Miller
2014-09-16 20:44 ` Alexei Starovoitov
2014-09-16 20:54 ` David Miller [this message]
2014-09-16 21:23 ` Alexei Starovoitov
2014-09-16 21:49 ` David Miller
2014-09-16 22:06 ` Alexei Starovoitov
2014-09-15 19:18 ` [PATCH v12 net-next 04/11] bpf: expand BPF syscall with program load/unload Alexei Starovoitov
2014-09-16 19:17 ` David Miller
2014-09-15 19:18 ` [PATCH v12 net-next 05/11] bpf: handle pseudo BPF_CALL insn Alexei Starovoitov
2014-09-15 19:18 ` [PATCH v12 net-next 06/11] bpf: verifier (add docs) Alexei Starovoitov
2014-09-15 19:18 ` [PATCH v12 net-next 07/11] bpf: verifier (add ability to receive verification log) Alexei Starovoitov
2014-09-15 19:18 ` [PATCH v12 net-next 08/11] bpf: handle pseudo BPF_LD_IMM64 insn Alexei Starovoitov
2014-09-15 19:18 ` [PATCH v12 net-next 09/11] bpf: verifier (add branch/goto checks) Alexei Starovoitov
2014-09-15 19:18 ` [PATCH v12 net-next 10/11] bpf: verifier (add verifier core) Alexei Starovoitov
2014-09-15 19:18 ` [PATCH v12 net-next 11/11] bpf: mini eBPF library, test stubs and verifier testsuite Alexei Starovoitov
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